In the fields of authenticating of physical articles it is known to rely upon an identifier for the article. An identifier based on a physical property of an unmodified surface of the article can be used (WO2005/088533). A system to implement article tracking and/or verification using such signatures can be a complex system involving equipment at multiple locations and depend upon a number of variable parameters.
The present invention has been conceived in the light of known drawbacks of existing systems.